In a tweet, Blankfein said: "Gary Cohn deserves credit for serving his country in a first class way. I'm sure I join many others who are disappointed to see him leave."
Cohn — a free trade advocate who opposed implementing tariffs — resigned from his post Tuesday night after Trump announced he would implement tariffs on steel and aluminum imports. Earlier on Tuesday, New York Times reported that Cohn would resign if Trump moved forward with his plan.
Bank of America also reacted to the news, with a spokesperson saying: "We thank him for his service to the country in helping drive pro-growth economic policies."
"He is a free trade markets guy and unfortunately until we know his replacement this adds another layer of uncertainty," said Art Hogan, chief market strategist at B. Riley FBR.
"This certainly solidifies the fact that Trump will move ahead with tariffs which in and of themselves may not be a major issue but if they make negotiations on NAFTA arduous or impossible that's a very major deal."
The news of Cohn's resignation sent ripples through global financial markets. U.S. stock futures pointed to sharp losses, with Dow Jones industrial average futures sliding 300 points. The euro rose to $1.2412 against the dollar, its highest level since Feb. 19.
Cohn was seen as a voice of reason in a White House that is seemingly in constant turmoil. His presence in the White House was also well-liked by investors given his track record on Wall Street. Prior to working in the Trump administration, Cohn was a top executive at Goldman Sachs and the heir apparent to Blankfein.
"Cohn has been a voice of moderation, he's been a voice of who understands markets, who understands investors, a voice that's committed to US playing a leadership role in the global system. His departure leaves an enormous void in that sense," said Nathan Sheets, chief economist at PGIM Fixed Income.